fix(mailer): fix delivery prevented with bcc

app/lib/balancer_delivery_method.rb

@@ -45,6 +45,7 @@ class BalancerDeliveryMethod
 
   def prevent_delivery?(mail)
     return false if mail[BYPASS_UNVERIFIED_MAIL_PROTECTION].present?
+    return false if mail.to.blank? # bcc list
 
     user = User.find_by(email: mail.to.first)
     return user.unverified_email? if user.present?

spec/lib/balancer_delivery_method_spec.rb

@@ -2,8 +2,8 @@ RSpec.describe BalancerDeliveryMethod do
   class ExampleMailer < ApplicationMailer
     include BalancedDeliveryConcern
 
-    def greet(name, bypass_unverified_mail_protection: true)
+    def greet(name, bypass_unverified_mail_protection: true, **mail_args)
-      mail(to: name, from: "smtp_from", body: "Hello #{name}")
+      mail(to: name, from: "smtp_from", body: "Hello #{name}", **mail_args)
 
       bypass_unverified_mail_protection! if bypass_unverified_mail_protection
     end
@@ -202,6 +202,13 @@ RSpec.describe BalancerDeliveryMethod do
         it { expect(mail).to have_been_delivered_using(MockSmtp) }
       end
     end
+
+    context 'when there are only bcc recipients' do
+      let(:bypass_unverified_mail_protection) { false }
+      let(:mail) { ExampleMailer.greet(nil, bypass_unverified_mail_protection: false, bcc: ["'u@a.com'"]) }
+
+      it { expect(mail).to have_been_delivered_using(MockSmtp) }
+    end
   end
 
   # Helpers